A. The access tier connects to the Internet and with lower tier Layer 2 devices to provide Layer 3 gateway services for the network.

B. The access tier provides network connectivity to end-user devices and other hosts, and enforces network access policy.

C. The access tier interfaces with lower tier devices and provides a high-speed interconnect with the north-bound WAN edge device.

D. The access tier relays packets between the lower tier Layer 2 devices and functions as the gateway to the upper tier device.